Cylinder of a rotary printing machine

ABSTRACT

The invention relates to the cylinder of a rotary printing machine in which cylinder two channels are arranged off-set from each other by an angle φ, said angle φ being determined depending on the moment of flexion f rib  inherent to the cylinder.

[0001] The invention relates to a cylinder of a rotary printing press inaccordance with the preamble of claim 1.

[0002] DE 198 03 809 A1 and JP 10-071694A disclose transfer cylinders ofa printing press with channels which are arranged offset by 180°.

[0003] The object of the invention is based on creating a cylinder.

[0004] In accordance with the invention, this object is attained bymeans of the characteristics of claim 1.

[0005] The advantages which can be achieved by means of the inventionprimarily lie in that the amplitude is minimized by passive vibrationdamping.

[0006] An exemplary embodiment of the invention is represented in thedrawings and will be described in greater detail in what follows.

[0007] Shown are in:

[0008]FIG. 1, a cylinder performing printing, having a split channelwith channel halves which are offset by an angle φ,

[0009]FIG. 2, a cylinder performing printing, having three channelsoffset by an angle φ,

[0010]FIG. 3, a cylinder performing printing, having four channelsoffset by an angle φ,

[0011]FIG. 4, an arrangement of channels in cylinders of equalcircumference performing printing,

[0012]FIG. 5, vibration amplitudes after overrolling the pair ofchannels (FIG. 1) in comparison to overrolling a single continuouschannel, or one extending over half the barrel width. The amplitudesrelate to an “isolated” overrolling, i.e. an amplitude amplification byprevious, not terminated overrolling is not taken into consideration.

[0013] The amplitude of the resultant total vibration within a definablerate of production range is minimized by the destructive interference ofthe vibration excited by sequential channel impacts. For this purposethe destructively interfering channel impacts must follow each otherclosely in order to best meet the interference conditions in regard toamplitude and phase relationships, for

[0014] (a) comparable amplitudes, i.e. the lowest possible vibrationdamping between the interfering channel impacts, lead to the greatestpossible obliteration,

[0015] (b) the phase relationship, i.e. the chronological distancebetween the interfering channel impacts should vary as little aspossible with the production rates in order to receive the obliterationover a wide range of production rates.

[0016] As represented in FIG. 1 to 3, each cylinder performing printinghas split channels.

[0017] The channels of each cylinder are offset from each other by adefined angle φ.

[0018] The angle of offset φ derived from the inherent bending frequencyf_(vib) of the cylinder and the rotation frequency f_(rot), at which theamplitude should be minimal, is calculated as

φ=(f _(rot) /f _(vib))*180°

[0019] In the course of the structural conversion, a deviation of up to±20% from the angle φ calculated in this way is permitted.

[0020] The channels of adjoining printing cylinders of equalcircumference are arranged in such a way that the respective channelsroll off on each other (FIG. 4).

[0021] The channels of adjoining printing cylinders, wherein a cylinderof double circumference is arranged next to a cylinder of singlecircumference, are arranged in such a way that the channels roll off oneach other during every, or every second, revolution of the cylinder ofsingle circumference.

[0022] Efficiency of the Vibration Damping:

[0023] In what follows, the channels represented in FIG. 1 and offset bythe angle φ calculated in accordance with the above equation are calleda “channel pair”. The resultant vibration amplitude after the channelpair has been rolled over, compared with the roll-over of a singlechannel extending over the entire barrel width, as well as in comparisonwith the roll-over of a single channel extending over half the barrelwidth, is shown by way of example in FIG. 5 in connection with an angleφ, which is optimized for the production rate of 70,000 pieces, forexample newspaper pages, per hour.

[0024] The vibration-technological advantages of a cylinder performingprinting and having a channel pair, over cylinders performing printingwith divided channels, offset by a different angle (mostly 90° or 180°)(called in what follows “conventionally staggered”) are twofold:

[0025] (1) Following the roll-over of the channel pair, the vibrationamplitude because of the destructive interference is lower by up to 60%than the one after the roll-over of a single split channel (FIG. 5).

[0026] (2) Following the roll-over of the channel pair, the excitedvibration has available the entire cylinder rotation time 1/f_(rot) fordecay while, with conventionally staggered cylinders, another channelimpact occurs within the same time. This is of importance in connectionwith high production rates in particular, wherein an amplitudeamplification because of the superimposition of non-decayed vibrationstakes place.

[0027] The cooperation of both effects increases the efficiency of thevibration damping past the amount represented in FIG. 5.

[0028] Comparison of the Structural Designs in FIGS. 1 to 3:

[0029] The first harmonic vibration of the bending vibration addssubstantially to the total vibration amplitude after roll-over of thechannel pair. Because the force introduction of the structural design inaccordance with FIG. 2—in contrast to the embodiments in accordance withFIG. 1 and FIG. 3—does not have the symmetry of the first harmonicvibration, the latter is much less excited in the embodiment inaccordance with FIG. 2. Opposed to this is the disadvantage of theembodiment in accordance with FIG. 2 that one channel impact takes place“on the outside”, and the other “on the inside”. This generally causesan excitation of varying strength of the base vibration, and therefore areduction of the vibration damping by destructive interference.

[0030] Moreover, the embodiment of FIG. 1 should be favored over theembodiments in accordance with FIG. 2 and FIG. 3 in view of thepossibilities of panoramic printing, as well as the simplicity ofintroducing the mechanical clamping channel elements.

[0031] As a whole, the embodiment in accordance with FIG. 1 thusrepresents the most favorable realization variation.

[0032] The cylinder is preferably designed as a forme or transfercylinder with channels for fastening printing plates or rubber blankets.

1. A cylinder of a rotary printing press, having at least two channelswhich are offset in respect to each other at an angle φ in thecircumferential direction, characterized in that the angle φ isdetermined as a function of the inherent bending frequency f_(vib) ofthe cylinder.
 2. The cylinder in accordance with claim 1, characterizedin that the angle φ is determined as a function of the rotationfrequency f_(rot) of the cylinder.
 3. The cylinder in accordance withclaims 1 and 2, characterized in that the angle φ has the dependence1.2*(f _(rot) /f _(vib))*180°≧angle φ≧0.8*(f _(rot) /f _(vib))*180°. 4.The cylinder in accordance with claim 1, characterized in that the angleφ has the dependence Angle φ=(f _(rot) /f _(vib))*180°.
 5. The cylinderin accordance with claim 1, characterized in that the selected rotationfrequency f_(rot) is laid out for the minimum vibration amplitude. 6.The cylinder in accordance with claim 1, characterized in that thecylinder is embodied as a forme or transfer cylinder.